Any structure requires the soil beneath it to have sufficient bearing capacity to support it. Otherwise, the settling or movement of the soil after the structure is built can cause it to fail. Many solutions to this problem have been developed, including injecting materials, such as expanding polyurethane material, into the soil beneath the structure (or where the structure will be built) to densify the soil and increase its bearing capacity. This is typically performed by placing tubing into the soil to the desired depth for injection of the material and then forcing the material through the tubing into the soil. The injection tubing often can extend some distance upwards from the surface of the structure built on the soil after the material has been injected.
Extension of the tubing above a structure may be a problem in certain situations, such as when the structure is a runway or road because the tubing may cause damage to tires or other equipment or harm to individuals. Even when the tubing is placed flush or slightly below the surface of the structure, movement of the soil due to natural phenomena such as frost heave or shrink-swell may push the tubing out of the soil so that it extends above the surface of the structure. Frost heave occurs when the soil expands due to freezing and then contracts when it thaws. Shrink-swell occurs when the soil expands or contracts due to heavy rainfall or drought. Tubing within the soil may be pushed out of the soil when it expands due to such phenomena and may not return to its original position within the soil when it contracts.
Removing tubing from the soil before the injected material cures is generally not an option due the very fast cure times of the materials used. Removing tubing from the soil during or after material curing can cause significant damage to the material and even destabilize the soil. It can also be very expensive, time-consuming, and difficult to remove the tubing from the soil during or after material curing due to forces exerted by the material on the tubing. These forces can cause the tubing to stretch or fracture (e.g. tear) when attempting to remove it, making it even more difficult to remove the tubing from the soil.